Power semiconductor devices combine high maximum current density with high voltage blocking capability. Typical power semiconductor devices have a vertical structure such that the load current flows between two opposite sides of a semiconductor die. In vertical devices the maximum current rating of the power semiconductor device is proportional to its area and the voltage blocking capability is positively correlated with the height or vertical extension of a drift region in the semiconductor die. In power semiconductor switches such as IGFETs (insulated gate field effect transistors) and IGBTs (insulated gate bipolar transistors) a gate electrode, which is capacitively coupled to body regions through a gate dielectric, controls a load current through the body regions. High blocking voltages result in strong electric fields near the gate dielectric such that instead of the properties of the drift region the dielectric strength of the gate dielectric may determine the voltage blocking capability of the power semiconductor device in case of semiconductors with high intrinsic breakdown field strength like SiC.
There is a need for further increasing the voltage blocking capability and for improving avalanche ruggedness of semiconductor devices without or with only low adverse impact on the current rating and on-state resistivity.